1. Field of the Invention
The present general inventive concept relates to a head adjustment method of an image forming apparatus, and more particularly, to a head adjustment method of adjusting images printed on a print medium by a plurality of independently driven heads in such a manner as to be aligned in relation to either a widthwise direction and/or a feeding direction of the print medium.
2. Description of the Related Art
In general, an image forming apparatus, such as an ink-jet printer, ejects fine droplets of print inks to desired positions on a print medium, such as a paper or a cloth, so as to print a predetermined color image on a surface of the print medium. A conventional ink-jet printer includes an ink cartridge for printing an image while reciprocating in a direction (i.e., in a widthwise direction of the print medium) that is at right angle to a feeding direction of the print medium. However, such a conventional ink-jet printer with an ink cartridge for printing an image while reciprocating across the print medium has a disadvantage in that the printing speed is very slow.
Recently, ink-jet printers have been developed to employ an ink cartridge having a plurality of print heads arranged over the entire width of a print medium, so that an image can be rapidly printed without causing the ink cartridge to reciprocate. Such ink-jet printers are also referred to as array print head type ink-jet printers.
A conventional array print head type ink cartridge includes a plurality of ink tanks, each for storing a print ink, a plurality of negative pressure adjustment units connected to the respective ink tanks, a plurality of print heads arranged in a predetermined pattern in the widthwise direction of a print medium, and an ink channel unit for supplying inks from the ink tanks to the print heads.
The ink tanks are mounted on a frame and contain various colors of inks, e.g., yellow (Y), magenta (M), cyan (C) and black (B) inks.
The negative pressure adjustment units are mounted on the underside of the frame and coupled to the respective ink tanks. Such negative pressure adjustment units produce negative pressure so as to prevent the leakage of ink.
The ink channel unit is connected with the negative pressure adjustment units and serves to supply inks discharged from the ink tanks and through the negative pressure adjustment units to each of the print heads.
The print heads are arranged in a predetermined pattern on and attached to the front face (i.e., the face that will be closest to the print medium during printing) of the ink channel unit. Each of the print heads is formed with a plurality of nozzles through which inks supplied from the ink channel unit is ejected onto a print medium, whereby an image is printed on the print medium.
Because an ink cartridge having the above-mentioned or other similar construction has a plurality of print heads, the spatial orientation or posture or geometry of the print heads may get varied when each of the print heads is assembled. In case of one or more such variations, an image printed on a paper by inks ejected from each of the print heads may be tilted or disoriented without being properly horizontally retained in the paper-feeding direction (hereinafter, to be referred to as “B” direction). In addition, when one or more print heads are misaligned in the widthwise direction of the paper (hereinafter, to be referred to as “A” direction), inks from different heads may overlap, thereby resulting in a darker spot on the paper, or misaligned heads may produce an empty space where no image is formed at a boundary area between two adjacent, but misaligned, print heads.
Therefore, it is desirable to provide a print head adjustment method in an array type inkjet printer or similar image forming apparatus for easily and rapidly aligning and adjusting the print heads.